In recent years, an electric vehicle has grown in demand from the viewpoint of global environment protection. However, because the capacity of a battery of the electric vehicle is not sufficient, a hybrid electric vehicle which uses an engine for driving assist or for power generation, and an electric vehicle which uses a fuel battery for power generation have been proposed.
The hybrid electric vehicle equipped with the engine for driving assist runs on a vehicle drive motor during urban driving and on the engine if the battery level is low or during suburban driving. On the other hand, the hybrid electric vehicle equipped with the engine for power generation runs on a vehicle drive motor and starts an engine to charge the battery if the battery level becomes low.
An air conditioner for a present electric vehicle generally drives a compressor (open type) of a refrigerant cycle on a vehicle drive motor. On the other hand, an air conditioner for the above-mentioned hybrid electric vehicle may cool a vehicle compartment inside by driving a compressor on an engine when the engine is in a drive condition. It may cool the vehicle compartment, when the engine is stopping, by driving the compressor using the vehicle drive motor, and, when a remaining battery level is low during the engine stopping, by starting the engine to drive the compressor.
However, two mechanisms are required: a mechanism for transmitting the rotation of an engine to the compressor and a mechanism for transmitting the rotation of a vehicle drive motor to the compressor, and also required is a clutch for switching these drive methods, increasing the system complexity and the cost.
On the other hand, a conventional air conditioner is structured so that a vehicle compartment inside may be heated by simply sending air to a heater core supplied with engine cooling water during heating operation, therefore when a temperature of cooling water is low, for example, at engine start-up, long time was required until an air-conditioning temperature in the vehicle compartment inside reaches a target temperature. At a low ambient temperature or the like, heating capacity was too small; therefore engine cooling water was heated with a PTC heater as an auxiliary heating means. Recent engines of other vehicle as well as the hybrid electric vehicle have been highly advanced and heat radiation from the engine has decreased; therefore the engine cooling water was heated with the PTC heater as an auxiliary heating means. Because an electric heater such as the PTC heater was used as an auxiliary heating means, heating efficiency was lower than that of a heat pump type heating apparatus.
In conventional technology, as shown in FIG. 10, a heat pump type refrigerant cycle includes a (sealed type) motor-driven compressor 104. A refrigerant-to-water heat exchanger 101 was newly attached to its refrigerant circuit as an auxiliary heating means during heating to drive the motor-driven compressor 104 with a first solenoid valve 102 closed and with a second solenoid valve 103 opened if an engine cooling water temperature is not higher than a preset temperature in the case of heating operation designated (refer to Japanese Patent Laid-Open No. 9-66722). The entire disclosure of Japanese Patent Laid-Open No. 9-66722 are incorporated herein by reference in its entirety.
This allows only the refrigerant-to-water heat exchanger 101 to function as a condenser and no refrigerant to be supplied to an evaporator 105. As a result, since no low-temperature refrigerant flows through the evaporator 105, the blowing air is not cooled. Therefore engine cooling water additionally heated by the refrigerant-to-water heat exchanger 101 flows through the heater core 106 to heat blowing air in a duct, so that heating capacity was capable of being enhanced without need for a PTC heater even if an engine cooling water temperature was low.
Such an air conditioner is additionally provided with the refrigerant-to-water heat exchanger 101 as a heating means to heat cooling water. To prevent refrigerant from flowing into the evaporator 105 in heating, solenoid valves 102, 103, pressure-reducing valves 108, 109, and an outdoor heat exchanger 107 are unavoidably necessary, which raises a problem of difficult space saving.
When an engine cooling water temperature is low at the time of heating, even if the refrigerant-to-water heat exchanger 101 is used as an auxiliary heating means, long time was required until a temperature of refrigerant passing through the refrigerant-to-water heat exchanger 101 rises high enough to start up the air conditioner; therefore there occurred a problem that it took long time for an air-conditioning temperature in a vehicle compartment to reach a target temperature, or that cool air was blown off from a heater core to the vehicle compartment inside.
Furthermore, if the evaporator 105 was frosted, defrosting operation was conducted, which caused intermittent operation, thus degrading climate pleasure.